The instant invention relates to crosslinked copolymers of (a) vinylic macromers containing perfluoropolyalkylether and polyalkylether segments with (b) minor amounts of vinylic comonomers and ophthalmic devices such as intraocular implants and contact lenses and particularly soft hydrogel contact lenses made therefrom. These devices possess an advantageous blend of desirable properties including (a) high oxygen permeability, (b) excellent wettability, (c) high mechanical strength, (d) flexibility, (e) optical clarity, (f) biocompatibility, and (g) are capable of being sterilized in boiling water. The perfluoropolyalkylether segments provide in large part the high oxygen permeability, the polyalkylether segments provide the wettability and the unique polymer structure provides the desired mechanical properties.
In general, most existing hydrogel soft contact lens materials are based on HEMA, also known as hydroxyethyl methacrylate or as ethylene glycol monomethacrylate, with one or more optional comonomers as described in U.S. Pat. Nos. 2,976,576, 3,841,985 and 3,985,697. Other hydrogels based on N-vinylpyrrolidone copolymers and acrylamide copolymers are disclosed in U.S. Pat. Nos. 3,639,524 and 3,929,741. These prior art hydrogel polymers generally suffer from several inherent problems (a) relatively weak mechanical strength, (b) low dissolved oxygen permeability or a combination of both. Most lenses are made by either of two procedures, one requiring costly lathing and polishing steps and the other using delicate spin casting techniques where polymerization, crosslinking, and shaping are done simultaneously.
Perfluoropolyalkylether segments have been proposed as constituents of contact lens materials. For example:
In U.S. Pat. Nos. 3,940,207 and 3,944,347 poly(perfluoropropylene oxide) oils were incorporated into a contact lens matrix. However, in this case the material is extremely hydrophobic and the oil can leach out.
In U.S. Pat. No. 3,542,461 a terpolymer is formed from hexafluoroacetone, tetrafluoroethylene and ethylene. The polymers so formed are in general of insufficient wettability and some are not of complete clarity.
In U.S. Pat. No. 4,440,918 and Eur. Pat. Appl. No. EP0084406, it is disclosed to make ophthalmic devices such as contact lenses from telechelic perfluorinated polyether polymers. These polymers are extremely hydrophobic and require the addition of a hydrophilic comonomer or surface treatment to improve wettability. Although an increase in wettability is described, the increase is generally insufficient to overcome the hydrophobic nature of the perfluoropolyether segments and to provide adequate patient comfort. Also, surface treatments are generally not permanent.
In Japanese Patent Applications Nos. 61-111308, 61-112047, 61-123609, 61-126052, 61-285425 and 61-285426, are described perfluoroalkylether containing polymers useful as raw materials for oxygen permeable devices and medical devices such as contact lenses. These polymers are of poor wettability and require the addition of hydrophilic comonomers or surface treatments to obtain the requisite wettability. Also, some of these materials have a tendency of being yellow in color.
In Eur. Pat. Appl. No. EP0253515 is described the use of a perfluoropolyether monomer for use in soft contact lenses. These materials are also extremely hydrophobic and need a substantial quantity of hydrophilic comonomer to obtain wettability and in addition require the inclusion of the N-vinylpyrrolidone comonomer to obtain clarity.
Perfluoropolyether monomers useful in condensation polymerizations are disclosed in Eur. Pat. Appl. No. EP0084406 and Jap. Pat. Appl. No. 61-166834. In the Japanese application a perfluoropolyether polytriazine material derived from a multivalent nitrile polymer is used in gas permeating materials such as contact lenses. These materials appear yellow in color. The perfluoropolyether monomers of both patent applications are hydrophobic and require the presence of a hydrophilic comonomer. In addition, condensation polymers are generally of poor quality for contact lens use because, for example, of the difficulty in obtaining a sufficiently high molecular weight with the concommitant desirable physical properties.
In Eur. Pat. Appl. No. EP0273449 is described aqueous dispersions of fluorinated polyurethanes containing ionic groups and their use for textile coatings.
It is an object of the present invention to overcome the disadvantages of the prior art by providing a modified perfluoropolyalkylether macromer which is inherently hydrophilic. This is accomplished by use of a block structure where the perfluoropolyalkylether block provides a substantial portion of the oxygen permeability properties and the polyalkylether block provides the hydrophilicity.
It is a further object to provide a perfluoropolyalkylether/polyalkylether macromer which can be crosslinked in the presence of a minor amount of another vinylic comonomer to form a soft water-swellable hydrogel contact lens having (a) high oxygen permeability (b) good wettability (c) high mechanical strength (d) flexibility (e) optical clarity, (f) biocompatibility and (g) capable of being sterilized in boiling water. It is a further object of the present invention to provide medium to high water content contact lenses obviating, or substantially reducing, the drawbacks of the prior art.
It is a further object of the present invention to provide a method of preparing such contact lenses by crosslinking a vinylic perfluoropolyalkylether/polyalkylether macromer with a minor amount of another vinylic comonomer in a solvent in a mold, such as a spin cast mold or a static cast mold, and equilibrating the resulting solvent swollen crosslinked contact lens in an aqueous medium.
A further object of the invention is to provide a method of correcting visual defects in the form of refractive errors by fitting to the patient's eye in need of the same, a corrective contact lens of such polymer.
These and other objects of the invention are apparent from the following detailed description of the invention.